Crallo was apparently the son of SS.
Sadwrn of Llansadwrn and Canna.
He is said to have been a pupil of his uncle, Illtud
at Llanilltud Fawr (Llantwit Major), before founding his own religious
community at Llangrallo, now Coychurch, in Glamorganshire. It adjoins his
mother's foundation at Llangan and he was eventually buried there.